The present invention relates to a control method for power-save modes of a serial interface of a data storage device that executes serial data communication.
Devices using various types of media such as optical disks and magnetic tapes are known as information recording and reproducing devices. Among them, hard disk drives (HDDs) have become popular as storage devices for computers to such an extent that they are one of the storage devices indispensable for today's computers. Further, not limited to computers, their application is widening more and more due to the superior characteristics with the advent of moving picture recording/reproducing devices, car navigation systems, removable memories for digital cameras and so on.
Each magnetic disk used in HDDs has a plurality of tracks formed concentrically and each track is partitioned into a plurality of sectors. In each sector, sector address information and user data are stored. Either data write to a sector or data read from the sector is enabled by a head element which accesses the desired sector according to the sector address information. A signal read out from a magnetic disk in a data read process is subjected to waveform shaping, decoding processing and other prescribed signal processing by a signal processing circuit before transmitted to a host. Likewise, data transferred from the host is subjected to prescribed signal processing by a signal processing circuit and then written to the magnetic disk.
For an interface to transmit data between the host and the HDD, such protocols as the SCSI interface or the ATA interface are used in general. In particular, the SCSI interface is used for many computers from the viewpoint of improved functions and economical cost of the interface, and it is also used as an interface for other types of storage devices such as an optical disk storage device. In a quest for improved recording density of recording media and improved performance, requirements for data transfer speed of ATA interfaces are becoming increasingly severe.
For the above-stated reasons, an ATA interface using serial data transfer has been proposed as a substitute for the conventional transmission system using parallel data transmission. The Serial ATA (SATA) standard is being formulated by the Serial ATA Working Group and is stated in detail, for example, in the Specifications (Non-patent Document 1, “Serial ATA: High Speed Serialized ATA Attachment Revision 1.0a” [Retrieved on Sep. 23, 2004] The Internet <URL: http://www.sata-io.org/specifications.asp>) prepared by the Serial ATA Working Group.
On the other hand, to reduce consumption power in HDDs, various power management methods have been proposed (for example, refer to the Patent Document 1, Japanese Patent Laid-open No. 2000-173152). Typically, an HDD is provided with a plurality of power-save mode, and switching is made to the prescribed power-save mode according to the number of commands from the host in a given period of time. In addition, for the SATA, power-save modes for serial interface have been proposed. For the power-save modes, two modes are proposed according to time required for recovery, that is, the Partial mode having shorter recovery time and the Slumber mode having longer recovery time.